1. Field of the Invention
The present invention relates to an image pickup apparatuses such as a digital camera or a video camera, and more particularly to an image pickup apparatus in which an image pickup element is movable in an optical axis direction.
2. Description of the Related Art
In an image pickup apparatus, an image pickup optical system constituted by a plurality of lens units is housed in a lens barrel to be held, and the shot image data (the output image) is obtained by performing a photoelectric conversion of an object image formed by the image pickup optical system using an image pickup element.
In the image pickup apparatus, due to a manufacturing error or an assembling error of lens units constituting the image pickup optical system or components constituting a lens barrel, any of the lens units may be inclined with reference to an optical axis of the image pickup optical system. In this case, on an imaging surface of the image pickup element, defocusing in an opposite direction of right and left or up and down may occur.
In order to solve such a problem, it is necessary to perform an inclination adjustment of each of the image pickup optical system and the image pickup element with reference to the optical axis (or a surface orthogonal to the optical axis) to perform a focusing on an entire imaging surface (see Japanese Patent Laid-Open No. 2004-325555). Moreover, in the image pickup optical system, it is necessary to perform other optical adjustments such as a decentering adjustment as well as the inclination adjustment. In performing the optical adjustment of the image pickup optical system such as the inclination adjustment or the decentering adjustment, a reference image pickup element for the adjustment that does not have the inclination or the decentering with reference to the optical axis is attached to the lens barrel to perform the optical adjustment of the image pickup optical system while an output image from the reference image pickup element is seen. Then, the reference image pickup element for the adjustment is replaced to an image pickup element for the imaging to perform the inclination adjustment of the image pickup element while an output image of the image pickup element for the imaging is seen.
On the other hand, in some image pickup apparatuses, the image pickup element is moved in the optical axis direction to be able to perform the zooming or focusing operation.
However, in the conventional image pickup apparatus in which the image pickup element is movable in the optical axis direction, the optical adjustment has to be performed in a state where the image pickup optical system and the image pickup element for the imaging that is movable in the optical axis direction, as well as a guide bar that guides the image pickup element in the optical axis direction, are built in the lens barrel. Therefore, as a common image pickup apparatus in which the image pickup element does not move in the optical axis direction, the optical adjustment cannot be performed only by using the image pickup optical system while the reference image pickup element is fixed and it was difficult to improve the adjustment accuracy.